My mom used a referee's whistle. There were 5 of us and the number of toots indicated which of the 5 she wanted (two toots for me). If we were outside playing in the neighborhood, we'd get alerted directly or indirectly from someone who was tired of hearing the whistle.
If it was dinner time and she needed us all, she'd blow 'Shave-and-a-haircut-two-bits'.
My dad whistled between his teeth. He was a prodigious whistler. As I recall, it was two tones alternating. Too bad we never measured how far away we could hear him whistling, because now I’m wondering. I’d guess half a mile though.
We had a 6" bell hung next to the back door. The same type as in churches where a rope pulls to get the bongs. It could be heard from a looooong way off. If it rang and we couldn't hear it, we were too far away from what was allowed.
If it was dinner time and she needed us all, she'd blow 'Shave-and-a-haircut-two-bits'.